Related Formula
The greatest integer function [u]$[u]$ changes value and experiences a step discontinuity at any point where its inner argument u$u$ takes on an integer value.
Core Logic
Analyze the potential points where either component function argument changes into an integer within the interval x in [0, 4]$x \in [0, 4]$.
- For [(x²)/(2)]$\left[\frac{x^2}{2}\right]$:
(x²)/(2)$\frac{x^2}{2}$ can range from (0)/(2) = 0$\frac{0}{2} = 0$ up to (16)/(2) = 8$\frac{16}{2} = 8$.
Integer values are reached at (x²)/(2) = 0, 1, 2, 3, 4, 5, 6, 7, 8$\frac{x^2}{2} = 0, 1, 2, 3, 4, 5, 6, 7, 8$, which means critical test locations are:
x = 0, √(2), 2, √(6), √(8), √(10), √(12), √(14), 4$$x = 0, \, \sqrt{2}, \, 2, \, \sqrt{6}, \, \sqrt{8}, \, \sqrt{10}, \, \sqrt{12}, \, \sqrt{14}, \, 4$$
- For [√(x)]$[\sqrt{x}]$:
√(x)$\sqrt{x}$ can range from √(0) = 0$\sqrt{0} = 0$ to √(4) = 2$\sqrt{4} = 2$.
Integer values are reached at √(x) = 0, 1, 2$\sqrt{x} = 0, 1, 2$, which means critical test locations are:
x = 0, 1, 4$$x = 0, \, 1, \, 4$$
Step 1: Audit Each Critical Point
Combine the set of test points within domain boundaries (0, 4)$(0, 4)$:
x in 1, √(2), 2, √(6), √(8), √(10), √(12), √(14)$$x \in \{1, \, \sqrt{2}, \, 2, \, \sqrt{6}, \, \sqrt{8}, \, \sqrt{10}, \, \sqrt{12}, \, \sqrt{14}\}$$
Let's evaluate the left and right hand limits at these specific values:
- At x = 1$x = 1$: [√(x)]$[\sqrt{x}]$ steps up while [(x²)/(2)]$\left[\frac{x^2}{2}\right]$ is constant $\implies$ Discontinuous.
- At x = √(2)$x = \sqrt{2}$: [(x²)/(2)]$\left[\frac{x^2}{2}\right]$ steps up while [√(x)]$[\sqrt{x}]$ is constant $\implies$ Discontinuous.
- At x = 2$x = 2$: Both functions experience an simultaneous integer step. Let's inspect:
- f(2) = [2] - [√(2)] = 2 - 1 = 1$f(2) = [2] - [\sqrt{2}] = 2 - 1 = 1$
- f(2^-) = [1.99] - [1.41] = 1 - 1 = 0$f(2^-) = [1.99] - [1.41] = 1 - 1 = 0$
Since LHL ≠$\neq$ value at point, it is Discontinuous.
Continuing this verification down the full combined list confirms that none of the step jumps cancel each other out.
Step 2: Sum the Discontinuity Points
Counting all isolated inner points within (0, 4)$(0, 4)$ yields exactly 8$8$ locations:
Total Points = 8$$\text{Total Points} = 8$$
Pattern Recognition
When two greatest integer functions drop steps simultaneously at the same point (like at x=2$x=2$), always write out the explicit left and right limits manually, as simultaneous steps occasionally step in matching directions and maintain unexpected continuity.
Chapter Mix
Class 12 Mathematics: Limits, Continuity and Differentiability